1. Field of the Invention
The present invention relates to a valve device for opening or closing a fluid passage and especially to such a valve device used as a purge valve for purging evaporated fuel stored in a canister mounted on an automotive vehicle.
2. Description of Related Art
In a valve device, pulsating waves are generated when a valve port in a fluid passage is abruptly closed, and the pulsating waves are transmitted to an upstream portion of the valve port. This phenomenon is known as a water-hammer phenomenon. For example, in a purge valve disposed in a passage between an engine and a canister for selectively supplying evaporated fuel stored in the canister to the engine, pulsating pressure waves are generated in the valve device when the passage is closed. The pulsating pressure waves are transmitted to the canister, and noises are generated in the canister.
JP-A-2001-295960 proposes a purge valve having a space for suppressing the pulsating waves. By enlarging a volume of the space, generation of the pulsating waves in the purge valve is better suppressed. However, there is a problem that a size of the purge valve becomes large by enlarging the space for suppressing the pulsating waves.
In addition, there is a recent tendency that an intake negative pressure of an engine becomes lower, and therefore, the purge valve becomes larger to provide a larger volume passage therein. In the large volume passage, an amount of the pulsating waves generated therein becomes larger. To suppress generation of the large amount of the pulsating waves, the suppressing space having a large volume is required, resulting in increase in the size of the purge valve. The same problem is similarly involved in valve devices other than the purge valve.